Two studies are in progress: A. Neonatal Liver Disease: Methods are in progress that will permit routine survey of neonates for the possibility of anicteric hepatitis. Detection of liver disease earlier in their course will (1) provide knowledge of their natural history, (2) the relationship to the occurrence of extrahepatic atresia, (3) permit better therapeutic approaches to the resolution of neonatal hepatitis and prevention of biliary atresia. B. Bile acid ester sulfation: the role of ester sulfation and renal excretion of bile acids when hepatic decompensation occurs is under investigation. Studies of naturally occurring cholestatic diseases in man and of a model being developed in the hamster is beginning to delineate patterns that may distinguish different types of liver disease and give insight on the determinants of the course of cholestatic liver disease.